This application is based on application No. 98-12659 filed in the Korean Industrial Property Office on Apr. 9, 1999, the content of which is incorporated hereinto by reference.
(a) Field of the Invention
The present invention relates to a method of recycling a cocatalyst for olefin polymerization conducted with a metallocene catalyst, and more particularly, to a method of recycling a cocatalyst for olefin polymerization conducted with a metallocene catalyst which can reuse cocatalyst for subsequent olefin polymerization such that the total amount of cocatalyst required can be reduced.
(b) Description of the Related Art
In 1976, Kaminsky of Germany reported that a metallocene catalyst shows high activity to olefin polymerization when methylaluminoxane is used for a cocatalyst (A. Anderson, et al., J. Herwing, W, Kaminsky, A. Merck, R. Motteweiler, J. Pein, H. Sinn, and H. J. Vollmer, Angew. Chem. Int. Ed. EngI., 15, 630, 1976).
This homogeneous catalyst has unique characteristics that distinguishes it from the conventional Ziegler-Natta catalyst. That is, this metallocene catalyst produces polymers with a narrow molecular weight and comonomer distribution and shows high copolymerization efficiency. Furthermore, by varying the type of ligand of metallocene catalyst, molecular weight or copolymerization degree can be changed, and, according to a molecular symmetry of the catalyst, stereoselectivity of the polymer can be controlled. These characteristics allow this metallocene catalyst can produce new polymers that can not be made with the conventional Ziegler-Natta catalyst. Hence, enormous efforts are being made in the research of this metallocene catalyst.
For activating this metallocene catalyst, however, an excess amount of aluminoxane, which is used for the cocatalyst, is required. Generally, a mole ratio of aluminoxane to metallocene is around 100-40000 to 1. The aluminoxane remains in the resulting polymer so that the physical properties of the resin are deteriorated. Furthermore, because the aluminoxane is very expensive, overall production costs are increased.
It is an object of the present invention to provide a method of recycling a cocatalyst for olefin polymerization conducted with a metallocene catalyst which can reuse the cocatalyst for subsequent olefin polymerization process such that the total amount of the cocatalyst reqiured can be reduced and production cost is minimized.
These and other objects may be achieved by a method of recycling a cocatalyst for olefin polymerization conducted by using a methallocene catalyst. The method includes the steps of polymerizing olefinic monomers by using a supported catalyst and a cocatalyst, separating the cocatalyst from the resulting polymer, and recycling the separated cocatalyst for subsequent olefinic polymerization. The supported catalyst is prepared by covalent-bonding a catalyst with a support, and the cocatalyst is dissolved in a suspension.